Degassing and grain refining of magnesium



Patented Feb. 15, 1949 DEGASSING AND GRAIN REFINING OF MAGNESIUM KossyStrauss, Birmingham, England, assignor to Foundry Services Limited,Birmingham, England, a British company No Drawing. Application January7. 1947, Serial No. 720,687. In Great Britain January 9, 1946 1 Claim.(Cl. 75-67) The present invention concerns improvements in or relatingto the degassing and grain refinement of magnesium and magnesium alloysand has for its object improved means for ensuring hexachloroethanecrystals. In a similar way,

chlorides, such as sodium chloride or potassium chloride can be used.

The vapor of hexachloroethane which is decomposed in the liquidmagnesium into chlorine,

that the agent employed for this purpose is efiec- 5 carbon and organicchlorine compounds with a tive over a sufficiently prolonged period oftime lower number of carbon atoms, effects the deto ensure that theprocess is completed. gassing and cleaning action in the metal and atAccording to the invention a solid organic chlothe same time the carbondeveloped during the ride such as hexachloroethane is employed as thedecomposition causes grain refinement. agent and is pressed into atablet with or without I claim: the additon of reactive or inertmaterials so that The process of treating magnesium and magthe reactioncan be prolonged and therefore the nesium alloys in molten state fordegassing and metal can be kept in contact with the gas for an refiningthe same, which consists in introducing extended period; preferably thetablet is thrust into the melt about 20% by Weight of sodium and held inthe molten metal while the reaction silico fluoride as an addition tohexachloroethane is proceeding. forming the remainder of a compositionin sub- Furthermore, additions to the heX-achlorostantially solid,compressed tablet form, and ethane which form a protective filmaround'the allowing said sodium silico fluoride to give offhexachloroethane crystals will prolong the resilico fluoride gas withinthe melt While sodium action still more. For instance hexachloroethanefluoride forms a residue and constitutes a proy be mixed With aflllOride S as Sodium, tective layer around hexachloroethane crystalspotassium or magnesium fluoride or a silicountil the'latter havecompletely vaporized within fluoride such as sodium potassium ormagnesium id lt; silico-fiuoride. As an example, if hexachloroossySTRAUSS ethane is mixed with 20% by Weight of sodiumsilico-fiuoride andthe mixture pressed into a tab- REFERENCES CITED let, the sodiumsilicofiuoride and hexachloroethane will decompose if this tablet isplunged gi g rgferences are of record m the into the liquid magnesium.The hexachloroethe 0 1S pa en ane is completely volatile whilst thesodium sili- UNITED STATES PATENTS cofluoride gives. ofi silicofluoriclegas and leaves sodium fluoride as a residue. This sodium fiuo- NumberName Date I ride which is in intimate mixture with the hexa- 7 11896301sterner-Rama 7, 1933 chloroethane forms a sort of protective layer2378699 Gunn June 1945 round the hexachloroethane crystals and onlyafter the heat has penetrated completely to the OTHER REFERENCES core ofthe tablet all the hexachloroethane will Battelle Memorial InstituteColumbus, Progress have vaporized. The same efiect can also be obp r nnv ti tion of Cast Ma nesium tained by using an inert material such asasbestos Alloys and 0 the EXiSting Foundry niqu s powder which forms aninsulating layer round the 0 and Practices, Declassified April 23, 1946;pp.

230, 234, 398 and 399.

